Immunological specificity and biological action of biliary glucagon-like substance in the rabbit

A glucagon-like substance named biliary IRG2000 whose molecular weight is approximately 2,000 was isolated by gel filtration from rabbit bile. This substance showed a strong crossreactivity as equivalent to 25.7 +/- 5.1 ng/ml of porcine glucagon in RIA with antiserum 30K specificity. Biliary IRG2000 brought about a significant increase and delayed the response of blood glucose level in coexistence with porcine glucagon, though it has no appreciable effect on the glucose level when administered singly to the mouse intraperitoneally. The response with the coexistence of these materials was far greater than when porcine glucagon was given alone. In Mortimore's type rat liver perfusion, a significant rise in glucose concentration in effluent was also observed when a mixture of biliary IRG2000 and porcine glucagon was perfused. The rate of 125I-glucagon degradation was found delayed in the presence of biliary IRG2000 when examined in the rat. Thus the increase and delayed response of glucose level in coexistence of porcine glucagon with biliary IRG2000 may be explained by a suppressive effect of glucagon degradation due to biliary IRG2000.